#include <bits/stdc++.h>

void solve() {
    int a, b;
    std::cin >> a >> b;
    int c = abs(a - b);
    if (c == 0) {
        if (a > 1) {
            std::cout << 2 << " " << a << "\n";
        } else {
            std::cout << "-1 -1\n";
        }
        return;
    }
    if (c == 1) {
        std::cout << "-1 -1\n";
        return;
    }
    int d = c;
    for (int i = 2; i * i <= c; ++i) {
        if (c % i == 0) {
            d = i;
            break;
        }
    }
    std::cout << d << " " << c << "\n";
}

int main() {
    std::ios_base::sync_with_stdio(false);
    std::cin.tie(0);

    int T;
    std::cin >> T;
    while (T--) {
        solve();
    }
}